Cathode heater support

ABSTRACT

A heater support loop for use in the multicathode gun of a cathode ray tube. The loop is made from a single piece of conductive material, which is ribbon-like in cross section and preformed into a generally triangular shape with pointed terminations, or apex portions, &#39;&#39;&#39;&#39;glassed&#39;&#39;&#39;&#39; into vitreous assembly rods. Three gaps are provided in the ribbon, intermediate the apexes of the loop, and the free ends adjoining the gaps are positioned to accept the connections of the filamentary heaters. Two of the apex portions of the loop are formed of short, straight runs of ribbon which form the point and interlock with the vitreous rod to prevent twisting of the ribbon material in the rod. The third apex is formed by free ends of the conductive ribbon disposed in closely spaced adjacency and each free end includes a portion bent outwardly and rearwardly from the adjoining end to provide for interlocking engagement with the embedding vitreous rod and extending into position to serve as a supply conductor for the loop.

States atent 1 1 Oct. 39, 1973 CATHODE HEATER SUPPORT [75] Inventor: Glenn Werst, Perkasie, Pa.

[73] Assignee: Philco-Ford Corporation,

Philadelphia, Pa.

22 Filed: May 25, 1972 21 Appl. No.: 256,979

Primary ExaminerDavid Schonberg Assistant Examiner-Paul A. Sacher Attorney-Robert D. Sanbom et al.

[57] ABSTRACT A heater support 100p for use in the multicathode gun of a cathode ray tube. The loop is made from a single piece of conductive material, which is ribbon-like in cross section and preformed into a generally triangular shape with pointed terminations, or apex portions, glassed" into vitreous assembly rods. Three gaps are provided in the ribbon,- intermediate the apexes of the loop, and the free ends adjoining the gaps are positioned to accept the connections of the filamentary heaters. Two of the apex portions of the loop are formed of short, straight runs of ribbon which form the point and interlock with the vitreous rod to prevent twisting of the ribbon material in the rod. The third apex is formed by free ends of the conductive ribbon disposed in closely spaced adjacency and each free end includes a portion bent outwardly and rearwardly from the adjoining end to provide for interlocking engagement with the embedding vitreous rod and extending into position to serve as a supply conductor for the loop.

4 Claims, 2 Drawing Figures CATIIODE HEATER SUPPORT BACKGROUND OF THE INVENTION This invention relates to electron guns, and is especially concerned with improvements in the filamentary heater support structure used in electron guns of color cathode ray tubes. In the manufacture of guns of this type, it has been customary to form the heater support loop of a plurality of pieces of wire or strap material. Adjacent spaced end portions of each said piece are glassed into adjoining assembly rods, while opposite adjacent end portions are welded to the heater connections. Such constructions have proven to be disadvantageous in that they involve a large number of individual welds, each of which increases the problems of assembly and is a potential source of arcing.

Recent improvements in this prior art apparatus have involved fabricating the ring or loop of a single piece of wire or ribbon which piece is generally triangular, when viewed in plan. Such a technique is taught and claimed in the copending disclosure of Thomas E. Chesla, bearing Ser. No. 256,980, filed May 25, 1972, and assigned to the assignee of the present invention.

It is the general objective of my invention to improve apparatus of this kind in such manner as to insure interlocking engagement between the corner or apex portions of the support loop and the vitreous rods within which said portions are embedded, and positively to prevent any twisting or sliding of the conductor with respect to the surrounding vitreous material. My apparatus is also featured by inclusion of free ribbon ends bent to form flying leads, where such leads emerge from the glass bead.

In achievement of the foregoing and other objectives and advantages of my invention, I provide a cathode heater loop formed of a narrow ribbon of conductive material and having three apex portions disposed in generally triangular array when the loop is viewed in plan, all in general accordance with the mentioned prior disclosure.

In particular accordance with my improvement, the apex portions are formed of short straight runs of ribbon which define points, when viewed in plan, and which points are embedded within the vitreous rod. This particular configuration is used at two of the apexes, the third being formed by free ends of the conductive ribbon disposed in closely spaced adjacency and bent outwardly and rearwardly from the adjoining end. This bending provides a termination which is generally pointed and which, taken in conjunction with the ribbon-like nature of the conductive material, positively prevents twisting or sliding of the conductor in the vitreous rod.

A heater support loop contemplated by this invention reduces the cost of the cathode ray tube gun by simplifying the fabricating processes, eliminating many welds and providing the highest possible stability for the conductor at the points of securement thereof with the glass beads.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevational view, on a substantially enlarged scale, with vitreous rods in section, showing the support loop after glassing thereof, and illustrating the manner in which the pointed apexes become embedded in the vitreous material of the supporting rod; and

FIG. 2 is a fragmentary elevational view on a similar scale showing the apparatus of this invention including the supported filamentary heaters and illustrating the structure in the position it occupies in the neck of a cathode ray tube.

DESCRIPTION OF THE PREFERRED EMBODIMENT With initial reference to FIG. 2, there is shown a cathode heater support loop 10 comprised of ribbonlike material and shown as mounted in the neck 11 of a color cathode ray tube 12. The neck is broken-away in the interest of clarity, and illustration of the apparatus is limited to the three vitreous insulating rods shown in section at l3, l4 and 15, and to the cathode heater loop 10 which is associated with and supported by said rods. As will be understood, a complete gun structurc would also comprise a battery of three electron guns, including grids and other elements, all of which would be supported by the vitreous rods. The various tube elements, including the cathode sleeves 16, 17 and 18 would all have suitable connection to the terminal pins 19 which extend externally of the tube. The cathode heaters are preferably of the known type which comprise twisted ceramic coated wire, see for example the wire 16a nested within the narrow, tubular sleeve or shell 16. Each heater has a pair of downwardly extending leads which are connected, as by welding, to the cathode heater loop 10. Two such leads are identified at 20 and 21, being connections for the heater contained within the enclosure 17.

In common with the apparatus of the mentioned copending disclosure, the loop 10 is generally triangular when viewed in plan and includes two comers or apex portions 22 and 23 and a third apex portion comprising free ends 24 and 25.

In the fabrication of a cathode heater structure of this kind a continuous loop is first provided as shown in FIG. 1, and the reversely bent apexes, as well as the third apex portion, are glassed into the supporting rods. By comparing FIGS. 1 and 2, it will be seen that the ribbon material, at central portions intermediate its apexes, is then severed for example along the lines of severance shown in FIG. 1 at 26, 27, and 28, in general accordance with the teaching of the copending disclosure. The ribbon material is then configured, in the region of the severed portions, to provide gaps by separating the adjacent severed ends thereof, see for example the gap between severed ends 29 and 30 (FIG. 2), to provide support locations for connection of the filamentary heaters. As will be understood without further description, the heaters are then connected in series circuit through the agency of the loop or ribbon 10, by welding the two leads of each such heater, e.g., leads 20 and 21, to a corresponding pair of spaced severed ends.

In particular accordance with my invention the corner portions which form apexes 22 and 23 comprise wire ribbon so bent reversely upon itself as to provide two short straight runs of ribbon leading to a point. See for example the runs 22a and 2212 which appear in FIG. 1. During glassing of the loop, these runs become interlocked with the vitreous material, as is clear from the drawing. There is virtually no possibility of an apex portion so configured, twisting or slipping with respect to the surrounding glass. Thus the ribbon is rigidly fixed as against both arcuate and vertical movement in the embedding material.

The third apex portion, that is the portion formed by the free ends 24 and 25, also presents this advantageous rigidity of construction. In this connection it will be noted that the ribbon is bent outwardly and rearwardly, as shown at 25a and 24a (FIG. 1) to provide straight runs which become embedded in the glass. These short straight runs are provided with extensions which lead back toward the center of the loop and terminate in the laterally extending wings 31 and 32. These wings constitute integral flying leads through the agency of which the loop and its filamentary heaters may be connected in the desired series circuit.

In one representative heater structure fabricated in accordance with this invention, the ribbon was of stainless steel 0.010 inch by 0.030 inch in cross section. The distance from the geometrical center of the loop to the apex portions was 0.375 inch while the spread between the spaced conductor portions, for example between the free ends 24 and 25, was about 0.10 inch. The short straight runs of ribbon should have a length suitable to permit the entire apex portion to be embedded in the vitreous rod, as illustrated.

It will be appreciated that during the glassing operation, the bead folds over and completely envelops the apex including the short straight runs of wire, for example the runs 22a and 22b and the runs 24a and 25a. In this way the ribbon is securely locked within the rod and a rigid heater loop is achieved with a minimum number of welds. The only welds required are those which secure the individual heater leads, for example the leads 20 and 21, to the loop.

I claim:

1. A cathode heater loop comprising: a narrow strip or ribbon of.conductive material having three apex portions disposed in generally triangular array when the loop is viewed in plan, and having gaps in each of three regions intermediate said apex portions, two of said apex portions comprising reversely bent ribbon portions configured toform generally pointed apex terminations when viewed in plan, and the third apex portion being formed by free ends of the conductive ribbon disposed in closely spaced adjacency, each said free end having an extension configured to extend outwardly and rearwardly from the adjoining end; three cathode heaters each having a pair of leads connected across a corresponding one of the gaps in said ribbon; and three rods of vitreous material each of which rods has one of said apex portions embedded therein.

2. Apparatus in accordance with claim 1, and further characterized in that said two apex portions are comprised of short runs of conductor embedded in the vitreous material and converging to a point.

3. Apparatus in accordance with claim 2, and in which said short runs are substantially straight.

4. Apparatus in accordance with claim 1, and further characterized in that said free end extensions which form the third apex portion each comprise a substantially straight run of conductor embedded in the vitreous material and terminating in connection leads extending out of said material. 

1. A cathode heater loop comprising: a narrow strip or ribbon of conductive material having three apex portions disposed in generally triangular array when the loop is viewed in plan, and having gaps in each of three regions intermediate said apex portions, two of said apex portions comprising reversely bent ribbon portions configured to form generally pointed apex terminations when viewed in plan, and the third apex portion being formed by free ends of the conductive ribbon disposed in closely spaced adjacency, each said free end having an extension configured to extend outwardly and rearwardly from the adjoining end; three cathode heaters each having a pair of leads connected across a corresponding one of the gaps in said ribbon; and three rods of vitreous material each of which rods has one of said apex portions embedded therein.
 2. Apparatus in accordance with claim 1, and further characterized in that said two apex portions are comprised of short runs of conductor embedded in the vitreous material and converging to a point.
 3. Apparatus in accordance with claim 2, and in which said short runs are substantially straight.
 4. Apparatus in accordance with claim 1, and further characterized in that said free end extensions which form the third apex portion each comprise a substantially straight run of conductor embedded in the vitreous material and terminating in connection leads extending out of said material. 